This invention relates to a twist-free texturing feed yarn of drawn thermoplastic filaments which differ in coloration or affinity for dyestuffs to obtain heather effects in fabrics. The invention is more particularly concerned with a yarn and a process for producing textured yarn which will provide a high contrast heather of low directionality or no directionality in fabrics.
Reese U.S. Pat. No. 3,593,513 discloses cospinning filaments of poly(ethylene terephthalate) and poly[ethylene terephthalate/5-(sodium sulfo)isophthalate] (98/2), or poly(hexamethylene adipamide), combining the filaments into a single composite yarn, drawing the filaments as an integral yarn, and further treating the drawn yarn to yield a finished yarn. False-twist texturing is mentioned. The patent teaches that the drawn yarn must have a degree of filament intermingling (DFI) of at least 65 percent and a difference in break elongation not exceeding 15 percent between the two types of filaments. A low contrast heather of low directionality is obtained when fabric made from the yarn is dyed with suitable dyes. For example, the poly(ethylene terephthalate) filaments can only be dyed with disperse dyes, the poly[ethylene terephthalate/5-(sodium sulfo)isophthalate] filaments can be dyed with disperse and basic dyes, and the poly(hexamethylene adipamide) filaments can be dyed with acid dyes.
Contrast refers to the ease with which the eye can distinguish between different colors in a fabric. At maximum filament intermingling, the different colors will appear to blend and provide a substantially uniform color. The Reese patent discloses a method of measuring the degree of filament intermingling (DFI). For the filament counts disclosed a DFI value of about 40 percent indicates no intermingling of the two types of filaments and 100 percent indicates the maximum obtainable filament intermingling.
A high contrast heather, corresponding to a DFI value of about 40 to about 60 percent, is desirable for many purposes. Mirhej U.S. Pat. No. 4,025,595 discloses that a moderately high contrast can be obtained by cospinning the two types of filaments into separate filament bundles, separately entangling each bundle to reduce subsequent filament intermingling between the bundles, drawing the bundles together to form a drawn yarn, and then passing the yarn through an interlacing jet to provide a DFI value of 60 to 63 percent. As shown in FIG. 3 of the patent, the interlace jet intermittently entangles the filament bundles together at cross-over points, the distance between which determines the directionality obtained in a fabric. Directionality refers to substantially parallel streaks of color formed between cross-over points by the separate bundles. The patent discloses that fabrics having average streak lengths of 0.5 to 1.5 cm have low directionality, fabrics having average streak lengths of 1.6 to 3 cm have medium directionality, and fabrics having average streak lengths greater than 3 cm have high directionality. The moderately high contrast heather provided by the process of that patent is accompanied by a medium to high directionality, even when the yarns are false-twist textured.
High contrast heather with low directionality has been provided by doubling two types of drawn filament bundles with true twist to provide a twisted yarn having a sufficient number of bundle cross-over points for low directionality. However, introduction of true twist is a low-speed process. It is desirable to avoid the expense of this additional operation.